Ultra high frequency signaltranslating stage



L 1949 D. H. MITCHELL 2,486,853

ULTRA HIGH FREQUENCY SIGNAL-TRANSLATING STAGE F iled Nov. 22, 1944 2 Shee'ts-Sheet 1 75 Confrol i a INVENTOR. jaw/agg 17 addarfiflww Q2? 4 L 1949 MITCHELL 2,486,863

ULTRA HIGH FREQUENCY SIGNAL-TRANSLATING STAGE Filed Nov. 22, 1944 2 SheetsSheet 2 Patented Nov. 1, 1949 ULTRA HIGH FREQUENCY SIGNAL- TRAN SLATING STAGE Donald H. Mitchell, Chicago, 111., assignor to Motorola, Inc., a corporation of Illinois Application November 22, 1944, Serial No. 564,675

Claims. 1

This invention relates to ultra-high-frequency signal translating stages and, while it ,is of general application, it is particularly adapted to be applied to a balanced push-pull ultra-highfrequency oscillator. The invention also relates to a balanced turning unit particularly suitable for use in such a stage or oscillator.

Heretofore there have been proposed numerous ultra-high-frequency oscillators and other signaltranslating stages embodying as the tuning means therefor a resonant transmission line, either of the concentric or parallel-conductor types, usually short circuited at the remote end. The parallel-conductor type has the advantages of simplicity and relatively lower cost, ease of tuning, and higher characteristic impedance. In general, the tuning of such lines has been effected by an adjustable sliding contact member which short circuits the line and varies its effective length, it being well known that such a line is resonant at a frequency of which the length of the line corresponds to one-quarter wave length.

While such arrangements theoretically are very satisfactory, in practice, at frequencies of 100 megacyoles upwards, it becomes difiicult to obtain the desired power output due to a number of factors principally involving the mechanical design of the apparatus. For example, such a structure generally involves a certain number of brackets, supports, and other structural elements of irregular shapes having points, corners, etc, which radiate and dissipate a considerable quantity of power. Further there are generally included a number of lead-conductors of considerable length from the resonant line to its associated vacuum tube, which conductors also radiate and dissipate power and introduce impedance and admittance at portions of the circuit where these parameters are undesired. For example,it is desira ble to concentrate all of the reactive impedance of the stage in the tuned circuit.

It is an object of the invention, therefore, to provides. new and improved ultra-high-frequency signal-translating stage including a tuning means of the resonant-line type by which one or more of the above mentioned disadvantages of the arrangements of the prior art may be avoided.

It is another object of the invention to provide a new and improved ultra-high-frequency signal-translating stage including tuning means i of the resonant-line type by means of which radiation and dissipation from portions of the structure and circuit, where they are inefiective, are reduced to a minimum.

.It is another object of the invention to provide a new and improved resonant-line tuning unit for use in an ultra-high-frequency signaltranslating stage which realizes the advantageous characteristics described.

In accordance with the invention, an ultra.- high frequency signal translating stage com prises electron discharge means includinga plurality .01 electrodes, a two-conductor resonant line having an open end, the conductors of the open end terminating individually closely ad.- jacent a pair of the electrodes and being electrically connected thereto. The stage also includes means for tuning the ,line comprising opposed condenser stator plates individually carried by the open-end conductors and a cooperative condenser plate common to the stator plates and adjustable relative thereto.

Further in accordance with the invention, an ultra-high-frequency stage of the type described comprises a push-pull oscillator comprising a pair of electron-discharge devices each having an anode, a cathode and a control electrode, the open-end conductors of the line terminating individually closely adjacent to, and being con.- nected to, a corresponding electrode preferably the .anode,.of .each of the pair of devices, The oscillator also includes regenerative coupling .between the respective anodes and control electrodes of the devices to produce sustained oscillations.

Further in accordance with the invention there is provided a balanced ultra-high-frequency tune ing unit suitable for use in the signal-translatingstage of the invention and comprising a two conductor resonant line having an open end, two opposed groups of condenser stator plates, each of the groups comprising at least two plates and being carried by .one of the open-end conductors and at least two cooperating condenser plates commonto the opposed stator plates and adjustable symmetrically relative thereto in a plane paralleltto a;plane of the stator plates. The cooperating plates are also individually adjustabletransversely to suchiplanetojbalance the uni-.17 and are adapted to be connected to a point of zero high-frequency potential.

Fora better understanding of the invention, to- 'gether with other and further objects thereof, reference is had to the following description taken in .connectionwith the accompanying drawings while its scope :will be .pointed out in :the

appended claims.

Referring now to the drawings, Fig. 1a is a perspective view of .an ultrahigh-ir equency si nal translating stage of the-oscillator type cm- 3 bodying the invention; Fig. 1b is a detail bottom view showing the connections of a resonant line to the electron discharge devices; Fig. 2 is a schematic circuit diagram of the oscillator of Fig. 1; while Figs. 3a and 3b are Plan and end views, respectively, of an alternative form of balanced resonant-line tuning unit.

Referring now to Fig. 1a of the drawings, there is shown a balanced ultra-high-frequency signaltranslating stage of the oscillator type comprising electron-discharge means including a plurality of electrodes and a balanced ultra-highfrequency resonant-line tuning unit therefor. Specifically, this stage comprises a balanced ultra-high-frequency push-pull oscillator including a pair of electron-discharge devices- I and II, shown in dotted lines for the sake of clarity. Each of the devices I0 and II is of the conventional triode type including an anode, a cathode and a control electrode or grid.

The ultra-high-frequency tuning unit comprises a two-conductor resonant line having one open end and preferably made up of two parallel cylindrical conductors I2 and I3, respectively. The conductors I2 and I3 at their open end terminate individually closely adjacent a pair of the electrodes of the electron-discharge means, specifically adjacent a corresponding electrode of each of said pair of devices, such as their anodes, and are electrically connected thereto. This is shown in Fig. 1b in which the conductors I2 and I3 are secured to a base I4 by upsetting or overturning their ends at I2a, I3a, respectively, at the same time engaging connection lugs I5 and I6, respectively, connected to the immediately adjacent connection lugs Illa and Ila associated with the tubes I0 and I I or their sockets, as the case may be. The remote end of the line comprising conductors I2 and I3 is shortcircuited by a pair of opposed clamping bars I'I adjustably secured to the conductors by means such as a bolt Ila. The electrical midpoint I'Ib of one of the shorting bars I! is connected to a source of space current B+ for the tubes II] and II through a radio-frequency choke I8a and is connected to ground through a radio frequency by-pass condenser I8b.

The ultra-high-frequency tuning unit also includes means for tuning the resonant line comprising opposed condenser stator plates individually carried by the open-end conductors near their open ends and a cooperating condenser plate common to the stator plates and adjustable symmetrically relative thereto. Specifically, the opposed stator plates comprise two opposed groups, each of the groups comprising at least two plates and preferably comprising U- shaped plates 20 and 2I folded closely about the open ends of the cylindrical conductors I2 and I3, respectively, to form two pairs of opposed stator plates 26a, 20b and 2Ia, 2Ib, respectively. The tuning means also includes two cooperating condenser plates common to the opposed stator plates. These cooperating plates are preferably in the form of a pair of parallel approximately figure-eight condenser rotor plates 22, 23 mounted on an insulated shaft or sleeve 24 and disposed between the pairs of plates 20a, 20b and 2Ia, 2Ib and between the plates of each pair. The plates 22 and 23 are rotatable or otherwise adjustable symmetrically relative to the stator plates 20a, 20b and 2Ia, 2Ib in planes parallel to the planes of the stator plates; that is, the axis of rotation of the shaft 24 is normal to the planes of the condenser stator plates. The rotor plates 22, 23 are also individually adjustable trans versely to the planes of the stator plates, that is, parallel to their axes of rotation, to balance the tuning unit. This transverse adjustment of the rotor plates 22 and 23 may be effected in any desired manner, preferably by bending or otherwise deforming one or both of the plates.

The ultra-high-frequency oscillator of Fig. la also includes a second two-conductor open-end resonant line, the open-end conductors being coupled individually to the cathodes of the devices I0 and I I. This second line is similar to the first line and the elements are given the same reference numerals with the added subscript I so that its description need not be repeated. The coupling from the open-end conductors I21 and I 31 to the cathodes of the devices Ill and II, respectively, is effected by means of the insulated cathode heating connections Illb, III) which pass through the tubular conductors I21 and I31, respectively, and beneath the base plate I4 to the lugs of the tubes II] and II, respectively, or of the sockets of such tubes, as shown in Fig. 11). One of each of the terminals Illb, III) is connected to a terminal I lai on the shorting bar I'Ia which, as indicated, is also connected to ground while the other of each of the pairs of conductors Illb, II b is connected to a source of cathode heating voltage indicated at A+, through a radio-frequency choke coil IS.

The condenser rotor plates 22, 23 and 221, 231 mounted on the common shaft 24 are adapted to be adjusted by any suitable mechanism such as the worm gear 3| and worm 32, which may be actuated manually or may be motor driven.

The oscillator thus includes the resonant line I2, I3 between the anodes of the devices I0 and II and ground and the resonant line I21, I31 between their control grids and ground, the resonant line, comprising conductors I 21 and I31, being common to the anode-cathode circuits and the grid-cathode circuits of the devices Ill and II. The oscillator also includes an output loop or turn 25 having arms lying closely adjacent the conductors I21 and I31 and the shorting bars I11 for deriving ultra-high-frequency oscillations from the line comprising the conductors I21 and I 31. A shield 33, shown in dotted lines for the sake of clarity, is disposed between the resonant lines I2, I3 and I21, I31 substantially to eliminate coupling between these lines.

The operation of the balanced push-pull ultrahigh-frequency oscillator described above will be best understood by reference to the simplified circuit diagram of Fig. 2 in which corresponding elements are given the same reference characters. The basic oscillator circuit is essentially a conventional one but utilizing resonant-line tun-.

ing units in place of the more usual tuning circuits comprising lumped inductance and capacitance. However, the circuit is somewhat unconventional in that the tuning means is divided between the anode and cathode circuits of the oscillator tubes, the line comprising the conductors I2 and I3 being connected in the anode circuit and that comprising the conductors I21 and I31 being connected in the cathode circuit. As indicated, the midpoint of the line comprising conductors I21, I 31 remote from the devices I0 and II is grounded. Similarly, the midpoint of the line comprising conductors I2, I3 remote from the anodes of the devices I0 and II is grounded through a by-pass condenser I8b. Each of the conductors I2, I3 and I21, I31 is approximately one-quarter wave length long, However, the eff ective length of the anode line I2, I 3, that is the length to the shorting bars H, H, is substantially less than that of the line I21, I31, this difference being introduced to compensate for the difference in the inherent anode-cathode capacitances of tubes I and II.

The grids of the device I 0 and II are directly interconnected and, since the potentials induced on the grids of the devices I0 and II by their respective anodes through the anode-grid capacitances Iilc, IIc, respectively, are substantially equal in magnitude and opposite in phase, due to the opposite phase of their anode potentials, these potentials tend to neutralize each other leaving the grids floating at substantially zero ultrahigh-frequency potential. The resulting oscillator circuit is substantially conventional, that is, the grids of each of the tubes being at substantially zero or ground potential and the anodes and cathodes fluctuating with respect thereto in opposite phase. While the exact nature of the oscillation-sustaining feedback is not fully understood, it is believed that the regenerative coupling required to generate sustained oscillations is due to the resonant line, comprising conductors I21 and E31, which comprises resonant self-impedances common to the grid-cathode and anode-cathode circuits of the tubes I0 and II. The output loop 25 coupled to the cathode resonant line I21, I31, is connected by way of a coaxial transmission line 21, or other suitable means, to the utilization circuit.

The tuning means for the lines I2, I3 and I21, I31, electrically are substantially conventional as illustrated in Fig. 2. However, the use of the resonant line conductors themselves as the supporting members for the condenser stator plates 2t, 2| and 201, 2I1 and the location of the resonant line conductors I2, I3 immediately adjacent the anode connection lugs IOa, IIa, of the tubes ID, I I, respectively, reduces to a minimum :the amount of undesired radiation and dissipation from irregular supporting brackets and elements and from conductor leads of substantial length.

At the same time, the tuning system is completely symmetrical so that the rotor plates 22, 23 and 221, 231 may, if desired, be connected to a point of zero ultra-high-frequency potential, such as ground. The auxiliary trimmer condensers 29, 30, connected in parallel with the tuning condensers 2023 and 201-431; aid in aligning the resonant frequencies of the two resonant lines. The system may be adjusted to balance by lateral bending or adjustment of one or more of the rotor plates 22, 23 and .221, 231 to adjust the capacitance curves of the two portions of the figure-8 condenser rotor plates and thus maintain a balance over the tuning range of the oscillator circuit. In general, such an adjustment can be made by means of two or more rotor plates disposed between fixed stator plates while the use of a single rotor plate between each pair of adjacent stator plates is ineifeotive since adjustment of the rotor plate nearer to one stator plate to increase the capacitance with respect thereto simultaneously and correspondingly decreases the capacitance of the rotor plate to the other stator plate.

While the operation of the oscillator has been described on the basis that the control grids of tubes Ill and II are maintained at substantially zero ultra-high-frequency potential, it will be understood that any suitable unidirectional or low-frequency control potential may be applied to the grids as through a radio-frequency choke coil 28. In one embodiment thegrids were-maim tained-at a slightly negative .unidirectionakpotential to block oscillations and were pulse modulated by positive pulses in order periodically to develop strong sustained oscillations and thus generate a series of pulses of ultra-high-frequency oscillations.

While it will be appreciated that the design constants of the ultra-high-frequency oscillator described may be varied within wide limits in accordance with the particular installation requirements, however, there follow by way of example only the essential circuit constants of one embodiment of the invention:

Vacuum tubes Ill, H, type 3A5/2 Conductors I2, I3-copper tubing, inch diameter, O. D., 3 inches in length shorting bars I'I, inch from remote ends of conductors I2, I3

Conductors I21, I31-copper tubing, inch diameter, 0. D., 3% inches in length shorting bar I11, A; inch from remote ends of conductors I21, I31

Condensers 20-23 and 201-231, max. capacitance 25 mmf., min. capacitance 10 mmf.

Trimmer condenser 29, 2.5 mmf.

Trimmer condenser 30, 5.0 mmf.

By-pass condenser I86, 1000 mini.

Tuning range, 200-250 me.

In Figs. 3a and 3b there is represented amodified form-10f the invention in which two simultaneously tunable resonant lines are arranged with'their open-end conductors in opposition and iI1':aXia1 alignment. In this case a U-shaped resonant line 40 having open-end conductors Ma and 40b is arranged in opposed relation to'a U- shaped resonant line AI having open end conductors Ma and Mb. Supported from the open ends or the conductors 40a, 40b are opposed groups of con-denser stator plates 40c and 40d, respectively. Similarly supported from the open ends of conductors 41111, Mb are .the .opposed groups of condenser stator plates tile and Md, respectively. Cooperating with the stator plates 40c, 40d are two pairs of rotor plates 42 and 4.3, each pair being disposed between adjacent ones of the .stator plates. Similarly pairs of rotor plates 44 and 45 are disposed between and cooperate with the opposed stator plates 4 I0 and Md, each pair being arranged between a pair Of adjacent stator plates. The rotor plates 42, 43, 44 and 45 are mounted on a common shaft .46 journaled in the short-cirouited ends of the resonant lines 40, II and 4.02 and Me, respectively, and adapted to be actuated by any suitable means such as a tuning knob 47. As indicated in Fig. 3b, the configuration of the stator plates and rotor plates is substantially the same as that of corresponding elements of the structure of Fig. 1a. The principles of operation of the balanced resonant-line tuning unit of Fig. 3b are entirely similar to those explained above with reference to Fig. 1a and need not be repeated. This construction has some electrical advantage in that there is minimum of coupling between the two resonant lines so that the requirement for shield- 7 modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. A balanced ultra-high-frequency push-pull oscillator comprising, a pair of electron discharge devices each having an anode, cathode and conrtrol electrode, a first two-conductor resonant line having an open end, the conductors of said open end terminating individuall closely adjacent the anodes of said pair of devices and being electrically connected thereto, a second two-conductor open-end resonant line the conductors of said open end being coupled individually to the cathodes of said pair of devices, means for tuning each of said lines comprising opposed condenser stator plates individually carried by said open-end conductors and a cooperating condenser plate common to said stator plates and adjustable symmetrically relative thereto, and means for simultaneously moving said condenser plates of said first and second resonant lines for simultaneously tuning said first and second resonant lines.

2. A balanced ultra-high-frequency push-pull oscillator comprising, a pair of electron discharge devices each having an anode, cathode and control electrode, a first two-conductor resonant line having an open end, the conductors of said open end terminating individually closely adjacent the anodes of said pair of devices and being electrically connected thereto, a second two-conductor open-end resonant line the conductors of said open end being coupled individually to the oathodes of said pair of devices, means for tuning each of said lines comprising opposed condenser stator plates individually carried by said openend conductors and a cooperative condenser plate common to said stator plates and adjustable symmetrically relative thereto, means for simultaneously moving said condenser plates of said first and second resonant lines for simultaneously tuning said first and second resonant lines, a regenerative coupling between the anodes and control electrodes of said devices to produce sustained oscillations, and an output loop coupled to one of said lines.

3. A balanced ultra-hig'h-frequency tuning unit comprising, an open-end resonant line comprising two parallel cylindrical conductors, two opposed pairs of condenser stator plates, each pair comprising a U-shaped plate folded around an open end of one of said conductors and supported thereby, at least two cooperating condenser plates common to said opposed stator plates and adjustable symmetrically relative thereto in a plane parallel to a plane of said stator plates, said cooperating plates being also individually adjustable transversely to said plane to balance said unit and being adapted to be connected to a point of zero high-frequency potential.

4. A balanced ultra-high-frequency tuning unit comprising, an open-end resonant line comprising two parallel cylindrical conductors, two opposed pairs of condenser stator plates, each pair comprising a U-shaped plate folded around an open end of one of said conductors, a pair of cooperating condenser plates disposed between said stator plates and adjustable symmetrically relative thereto in a plane parallel to a plane of said stator plates, said cooperating plates bein also individually adjustable transversely to said plane to balance said unit and being adapted to be connected to a point of zero high-frequency potential.

5. A balanced ultra-high-frequency tuning unit comprising, an open-end resonant line comprising two parallel cylindrical conductors, two opposed pairs of condenser stator plates, each pair comprising a U-shaped plate folded around an open end of one of said conductors, a pair of approximately figure-8 condenser rotor plates disposed between said opposed stator plates and adjustable symmetrically relative thereto in a plane parallel to a plane of said stator plates, said cooperating plates being also individually adjustable transversely to said plane Ito balance said unit and being adapted to be connected to a point of zero high-frequency potential.

DONALD H. MITCHELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,060,508 Kozanowski Nov. 10, 1936 2,102,426 Lindenblad Dec. 14, 1937 2,143,891 Lindenblad Jan. 17, 1939 2,159,782 Conklin et a1 May 23, 1939 2,192,711 Lindenblad Mar. 5, 1940 2,193,500 Usselman Mar. 12, 1940 2,302,369 George Nov. 17, 1942 2,366,750 Pray Jan. 9, 1945 2,367,681 Karplus et al. Jan. 23, 1945 2,384,504 Thias Sept. 11, 1945 2,391,917 Newkirk Jan. 1, 1946 2,413,018 Willoughby Dec. 24, 1946 OTHER REFERENCES Radio Amateurs Handbook, 1940 edition, pages 409411. 

